This invention relates to the controlled atmospheric storage of fresh produce (ie., fruit, vegetables, and flowers), and especially to a package using cellophane and uniaxial microporous film panels that controls the atmosphere surrounding the packaged produce to improve retention of produce freshness without moisture build-up.
In the field of Controlled Atmosphere Packaging (CAP), it has been established that the shelf life of fruits and vegetables can often be extended by enclosing them in slightly permeable films or containers. If the permeability of the container material(s) is chosen properly with regard to the respiration rate and weight of the produce, the O.sub.2 and CO.sub.2 levels within the container can be made to equilibrate at levels much different from the normal atmospheric levels of 21% of O.sub.2 and 0.03% of CO.sub.2. If, for example, the atmosphere in a container of strawberries is made of equilibrate at about 5% of O.sub.2 and at about 16% of CO.sub.2, certain aspects of the strawberry appearance/flavor/texture are either improved or degraded at a slower rate; it is said that the "shelf life" has been extended.
Some produce items, such as mushrooms and strawberries, liberate water vapor very rapidly due to rapid respiration and/or rapid evaporation from the produce surface. When packaged by controlled atmosphere packaging (hereinafter referred to as "CAP"), an undesirable excessive amount of condensation of moisture is on the surfaces of the produce and on the package. This moisture condensation and high humaidity cause the problems of water-logging and a poor slimy surface txture on mushrooms.
Prior to the present invention, the moisture problem in CAP containers has been dealt with in several ways. U.S. patents 4,079,152 and 4,423,080 disclose the insertion of a packet formed from water permeable uncoated cellophane film or Tyvek film (a film formed from polyethylene marketed by E. I. duPont de Nemours & Co.) containing a desiccant and CO.sub.2 absorber (such as calcium chloride, lithium chloride, ethylene glycol, silica gel, calcium hydroxide, etc.) into CAP containers; the packet absorbs moisture and CO.sub.2 from the container's environment preventing mold growth or other respiratory injury to the produce. U.S. patent 3,795,749 discloses wrapping lettuce in a plasticized polyvinyl chloride film that permits CO.sub.2 to freely escape from the package and allows some moisture to escape but retains enough moisture in the package to prevent the lettuce from drying out.
CAP containers using a cellophane or coated cellophane film layer in combination with another film layer such as polypropylene or polyethylene for controlling the atmosphere in the container are disclosed in U.S. patents 4,055,672 and 3,574,642.
Nonw of this prior art discloses the instant invention.